248 ELEMENTS OF ELECTRICAL ENGINEERING. 



a lead plate with a finely corrugated surface is subjected to the 

 action of a suitable acid bath which converts the surface layers 

 of the metal into active material by corrosion. Plante' s original 

 process was to expose the lead plates to the action of dilute sul- 

 phuric acid, the corroding action of which he accelerated by mak- 

 ing the plates alternately anode and cathode. In the modified 

 Plante processes * now used the corrosion is accelerated by the 

 addition of a small percentage of a lead dissolving acid, such as 

 nitric acid or acetic acid. 



In the Faure process the active material is manufactured in 

 bulk by any suitable chemical process and introduced mechanically 

 into the interstices of the lead grids, f Faure' s original process 

 which is still extensively used was to apply the active material 



in the form of a paste made by wetting 

 litharge or a mixture of litharge and 

 red lead with dilute sulphuric acid. 



The grid of the Gould storage bat- 

 tery, which is shown in Fig. 144, is an 

 example of a grid made by the acceler- 

 ated Plante process. Thick plates of 

 metallic lead of the desired shape are 

 placed between rapidly rotating spinning 

 Fig 144 rolls which raise thin fins of the metal on 



the faces of the plate. A central web and 



cross-ribs of untouched lead are left to give the grid the requisite 

 strength and conductivity, and the active material is formed over 

 the greatly increased surface of the fins by a process of corrosion. 

 Each spinning roll consists of a large number of thin steel disks 

 with thin spacing washers between, all clamped rigidly together 

 on a shaft. The positive grid always gives more trouble from 

 buckling and it is weakened by corrosion much more rapidly 



* See Storage Battery Engineering, by Lamar Lyndon, Chapter XVI. 

 t A variety of grids made by modifications of the Faure process are described by 

 Lyndon, Storage Battery Engineering, Chapter XVII. 



